[SCCC] portable contesting power

[Bob Grubic]

Drew,

I enjoyed your email a lot. Portable operating is for me too. Thanks for
starting the ball rolling.

Good luck.

73,
Bob NC6Q

On Sat, Jan 2, 2021, 9:59 PM Peter Putnam <ni6e at twc.com> wrote:

> Drew,
>
> I've found several common Icom radios (IC-706, IC-7000) that are not
> happy with your anticipated supply voltage range of 12.0 to 12.8 volts.
> Complaints range from distorted audio to doing a complete power-on reset
> on the first voice peak. Voltage drop in the wiring from the battery to
> the radio plays a role in this issue, so your mileage may vary...
>
> You might find the range of 13.0 to 13.8 to be more suitable. A series
> set of 6 LTO (Lithium-titanate) cells initially charged to 14.0 volts is
> worth considering.
>
> An MPPT solar controller for a "12-volt" system barely outperforms a PWM
> controller when the open-circuit panel voltage is in the range of 21 to
> 22 volts, typical for a 100 watt panel. The MPPT controller becomes the
> obvious choice when the panel voltage is two or three times higher than
> the battery voltage.
>
> Don't be tempted to use one of the $15.00 PWM controllers from China.
> They connect the positive panel output to the positive terminal of the
> battery and do the switching on the negative terminals, making a common
> ground connection impossible.
>
> Paralleling solar panels gives disappointing results. If one panels
> voltage is a few millivolts higher than the other, it will deliver most
> of the output while the other panel loafs along. My experiments with two
> identical 150 watt panels in parallel maxed out at only 200 watts. You
> get what you expect if you put the panels in series, but that requires a
> controller that can handle the higher input voltage. The Morningstar
> SS-MPPT-15L, for example, can accept panel voltages up to 60 volts,
> efficiently accommodating two 100 watt panels in series.
>
> 73,
> Peter
> NI6E
>
>
>
> On 1/2/2021 12:54 PM, Drew Arnett wrote:
> > I've been burning holiday time researching a few things.  Due to not
> > fantastic radio home location, portable is the way to go for me for
> > any serious contest effort.  I haven't purchased a genset, yet.  I had
> > a hypothesis that battery or battery + solar might be a good move.
> >
> > I'm only considering LiFePO4 (aka LFP) and not lead-acid.  Lead-acid
> > are cheap as heck, but wow, those things are just what you need for
> > boat ballast.  Lifetime is supposed to be a lot better for LFP.
> > (Thousands of cycles!  How do I recoup the $ value of all the unused
> > cycles if I only use a dozen times a year contesting?  Email me if you
> > have good ideas!)  No need for battery V boost converter.  90% depth
> > of discharge at 12.0 V and 12.8 V roughly for much of the discharge.
> > I think battery efficiency for a cycle is 90%.
> >
> > I'm factoring in a lot of things, but still rough numbers.  Need some
> > margin, but margin is easy to get.  Reduce PA power by 1 dB is 80% for
> > example.  Assuming camping someplace without shade during day and
> > sunny skies, etc.  Overall, I think my ballpark figuring isn't far
> > off.
> >
> > Baseline:
> > Renogy 100 amp-hour 64 lbs $212 @ Home Depot
> > --> $2/amp-hour
> >
> > LFPs data points:
> > Renogy 100 amp-hour 26 lbs $765 shipped, can be paralleled
> > --> $8.5/amp-hour, figuring 90% usable depth of discharge
> > Renogy 170 amp-hour 48.5 lbs (tempting!) $1275 shipped, can be
> > paralleled (but why?)
> > --> $8.3/amp-hour
> >
> > Does Renogy offer discount for will-call at their SoCal location?  For
> > hams like that other brand?  For group buy quantity?  I haven't asked,
> > yet.  I picked Renogy at random, mostly because Home Depot sells them.
> >
> > These batteries have BMS to keep the battery healthy.  Can be set to
> > shelf mode for safety, perhaps during transport, assembly,
> > disassembly.  They offer an inexpensive display panel to show load,
> > capacity and current charge/load rate.
> >
> > If willing to try random brands, I see stuff as low as sub $6/amp-hour
> > shipped.  (If someone has info or has done homework, let me know,
> > please!)
> >
> > For solar, I don't have time this year to chase down RFI.  Genasun has
> > a stellar reputation.  (If someone has info or has done homework, let
> > me know, please!)  So, another data point:
> >
> > Genasun GV-10-Li-14.2V $135
> >
> > That wants to be paired with a 100W panel.  (Their support is good,
> > talking to them about options.)
> >
> > Grape 100W panel at Home Depot $72
> >
> > No RFI to mitigate (I hope!) unlike even the great Honda gensets.
> >
> > For each panel/controller pair above, can supply load and/or charge at
> > up to 100W per set.  Parallel those to retop batteries.
> >
> > Using a couple of web tools, I was able to get the amount of charging
> > for fixed position (tipped per time of year) or move several times
> > through the day for SoCal for some of the big events during the year.
> > Ranges from 5.3 to 8.7 equivalent hours a day.  (Nice to be in SoCal!)
> >
> > Interestingly, the time of day of start does have an impact on
> > battery/panel tradeoff.  FD is about the easiest and CQ WW the
> > toughest out of the events I analyzed.
> >
> > Assumed 90W load.  RPi/KX3/KXPA100 100W TX 25% duty cycle
> >
> > 100 amp-hour + 0 W panel --> 12.9 hours runtime for $764
> > 170 amp hour + 0 W panel --> 21.9 hours runtime for $1274
> > 200 amp hour + 0 W panel --> 25.7 hours runtime for $1528
> >
> > A pair of 100 amp-hour batteries paralleled for 24 hour portable
> > contests looks not bad at all.  Just top off a month before you go.
> > Use $200 of solar charge capability at home.  Hard mount in your
> > vehicle?  Takes up little space.  Drag out the panel, too, to run the
> > fan during the day.
> >
> > FD (24 hr) 100 amp-hour + 100 W (sleep 2 hours)
> > SS (24 of 30) 100 amp-hour + 200 W (sleep a bit less than 4 hours the
> > first night)
> > CQP (24 of 30) 100 amp-hour + 100 W (designed for solar!, sleep the
> > same 5 hours as everyone else)
> > IARU HF (24) 100 amp-hour + 200 W (maybe 2 hours of downtime, not
> > designed for solar for our time zone)
> > CQ WPX (48) 100 amp-hour + 200 W (sleep 5 hours a night)
> > CQ WW (48) two choices:
> > 100 amp-hour + 300 W (39 hours, sleep 5 hours a night)
> > 200 amp-hour + 200 W (don't sleep)
> >
> > There may be a mistake above.  I'd calculate before a specific event,
> > anyway, as I'd want planning notes.  Tilt angle, power budget over
> > time & strategy, etc.  (If anyone knows of a writeup of this sort of
> > analysis that I could use instead of doing this myself, let me know!)
> >
> > No RFI.  Possibly very little bulk, at least for 24 hour contests.  A
> > couple of panels for longer contests.  No RFI.  No gas can.  No gas
> > engine maintenance.  Bulk of a couple of panels versus generator &
> > jerry can.  (Those thin monocrystalline panels offered by several
> > vendors for $200 for 100W would be easier to stow.)  More criteria for
> > choosing location.  More susceptibility to weather.  :-)
> >
> > Really no significant price difference, unless scaling up for CQ WW
> > (in the dark of winter) or for other reasons.
> >
> > No QRO, but as a CW op, I'd be thinking class E amplifiers.  (How come
> > no commercial class E CW amps on the market?  So great for portable
> > power.  And think about the lack of heatsink/fan/weight/bulk.
> >
> > Hmm.  If I'm writing my own contest logging software, I could have it
> > display the power situation, too.  Perhaps throttle the rig power 10
> > or 20% when needed.  Etc.  :-)
> >
> > Best regards,
> >
> > Drew
> > n7da
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>
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